The properties and reaction mechanisms of a number of flavoprotein enzymes will continue to be explored. These have been chosen so that they are representative of each of the major classes of flavoproteins. Thus, glucose oxidase, D-amino acid oxidase and lactate oxidase are examples of oxidase flavoproteins which are being studied. Flavodoxin as a representative example of an electron transferase, D-lactate dehydrogenase as a representative transhydrogenase and p-hydroxybenzoate hydroxylase as a typical monooxygenase are all being studied. Finally, xanthine oxidase is being investigated as an example of complex flavoprotein with multiple redox groups. As in the past, extensive use will be made of steady state kinetics coupled with rapid reaction kinetic studies. This permits the identification and characterization of reaction intermediates, and the feasibility of their involvement in catalysis. The major thrust of the research project is exploring the uses of artificial flavins, in place of the natural coenzymes, in determination of mechanism, and as probes of the active site regions of the individual enzymes.